The trend at Bank of New Zealand in the recent December 2010 quarter was similar to Westpac's, with deposit growth outpacing a small increase in the loan book.However, unlike Westpac, BNZ's asset quality, as measured by a rise in 90-day loans, an increase in provisions and an increase in impaired assets, worsened during the quarter.Corporate exposure was largely to blame, with 90-day past due corporate assets rising to NZ$93 million, from NZ$80 million, and impaired assets growing to NZ$334 million, from NZ$292 million. Provisions on corporate loans rose to NZ$194 million, up $20 million.Gross loans rose 0.5 per cent, to NZ$55.65 billion, thanks to a small increase in housing loans and other term lending. Deposits grew 5.1 per cent, with a rise seen in both term deposit and interest-bearing demand deposits.Operating profit rose to NZ$215 million, from NZ$182 million for the corresponding   December quarter of 2009. However, net profit almost halved, to NZ$150 million, from NZ$271 million, as the previous year's figures were distorted by income tax credits related to structured finance transactions.